Removal of common pharmaceuticals present in surface waters by Amberlite XAD-7 acrylic-ester-resin: Influence of pH and presence of other drugs

Pharmaceutical products are often present in wastewater treatment effluents, rivers and lakes. A wide variety of drugs have been found in waterways of many countries, including analgesics, antibiotics and antiepileptics. The adsorption of four common pharmaceuticals present in surface-waters, trimethoprim (antibiotic), carbamazepine (antiepileptic), ketoprofen and naproxen (analgesics) onto Amberlite XAD-7 (an acrylic ester resin) has been investigated. Adsorption experiments were carried out at different pH conditions and the experimental equilibrium data were fitted to the Langmuir, Freundlich and Dubinin-Radushkevich models. For the same experimental conditions (pH 7) the estimated adsorption capacities are from 97 mg g(-1) for carbamazepine >54 mg g(-1) for trimethoprim >45 mg g(-1) for ketoprofen and approximate to 43 mg g(-1) for naproxen. The influence of adsorption pH was established for each compound. The investigation indicates that the mean sorption energy (E=8.3-10.1 kJ mol(-1)) characterizes a physical adsorption and the surface of the resin is energetically heterogeneous. On the other hand, the work studies the effect of the presence of other drugs in solution on the individual adsorption process. The comparison of Freundlich-parameters shows that the adsorption capacity decreases as expected for neutral and acidic drugs and increases for the case of trimethoprim (a basic drug). (C) 2010 Elsevier B.V. All rights reserved.